    Patent document 1: JP-H11-51684 A corresponding to U.S. Pat. No. 6,108,604    Patent document 2: JP-2001-317956 A corresponding to US-2001/0041962
Conventionally, a navigation apparatus has a route guidance function to navigate a driver of a vehicle along a route from a departure point to a destination.
The driver can drive the vehicle based on the route guidance to thereby reach a destination without getting lost. A route to a destination may include a rotary (or called a traffic circle) as a guidance target. Such a rotary often has a configuration more complicated than that of a typical intersection; thereby, if a rotary is included in a guidance route, it may be difficult for a driver or user to confirm an exit route from the rotary. Accordingly, when performing a route guidance in a rotary, a display style is changed from a right/left turn branch display for performing a usual road guidance other than a rotary to a rotary guidance display for indicating an exit route using a picture or image representing a configuration of the exit route.
Such a rotary guidance display is provided in a navigation apparatus disclosed in Patent document 1 or Patent document 2 while adopting a method for indicating a road via which a vehicle should exit from the rotary. Patent document 1 adopts a technique to determine a branch direction from a relative direction between a road entering a rotary and a road exiting the rotary. Patent document 2 adopts a technique to indicate what number an exit road is after entering a rotary.
In the above rotary guidance display in Patent document 1 and Patent document 2, an entrance road and an exit road of a rotary are always illustrated by a rotary guidance display. Herein, the rotary guidance display cannot illustrate an exit road or exit route inside the rotary. For instance, a turn by turn (TbT) function is provided which can display only a picture of a specific pattern stored in a map disk or microcomputer. In such a turn by turn function, only a picture to illustrate an exit route advancing outward of a rotary is prepared; thus, when an exit road from the rotary advances inward of the rotary, such an exit road advancing inward of the rotary cannot be displayed inside of the rotary. Accordingly, the driver may not be provided with a correct route guidance in a rotary having an exit route advancing inward of the rotary.